Scientists move closer to male pill

Researchers in the US are exploring a new direction in male contraception after finding a molecule that makes sperm infertile without using hormones.

Following successful tests in mice, researchers wrote in the journal Cell that the molecule, known as JQ1, can pass the barrier between a man's blood vessels and sperm-producing cells in his testes.

The result is a reversible contraceptive effect that could pave the way for a male "pill" that does not rely on hormonal changes, and which does not affect libido and does no permanent damage to male fertility.

A research team led by Martin Matzuk of Baylor College of Medicine (BCM) in Houston, Texas, and James Bradner of Dana-Farber Cancer Institute and Harvard Medical School in Boston found that the JQ1 molecule can gain access to a key protein involved in sperm production, disrupting it and making the sperm infertile.

Matzuk told a news conference that the tests in mice had shown that the process was also reversible, because the sperm returned to normal once the drug ceased to be administered.

The molecule works by targeting a protein that is found only in the testis and helps control the way in which the genes make sperm production happen.

Taking place in the nucleus of the sperm cell itself, the molecule blocks a process known as chromatin remodelling by binding to the protein, known as BRDT.

The researchers initially discovered the effects of JQ1 in a test tube, and later carried out an 18 month study in mice, which were found to have lower sperm counts and less mobile sperm after being injected with a solution of JQ1 compared with a control group that did not receive the drug.

While mating behaviour carried on as normal, the mice given JQ1 were not fertile enough to engender offspring, because they had sperm counts that were below the fertilisation threshold in all mammals, including humans.

While a contraceptive pill for men based on JQ1 is unlikely, because the molecule binds with proteins that are similar to BRDT, it had shown that BRDT was a good target for future work on male contraception, Matzuk said.

He told reporters that the study would also provide the team with useful information for future research efforts and drug development.

According to Allan Pacey, senior lecturer in andrology at the University of Sheffield, most trials of male contraceptives so far have tried blocking sperm production by manipulating the male hormone testosterone.

He said no-one had yet tried an approach that bypassed the hormonal route entirely.

Meanwhile, Moira O'Bryan, head of male infertility at Monash University in Australia, said the team's findings could have "major scientific and social impacts."

She said a version of the JQ1 molecule could eventually find its way into a male "pill", given the similarities between sperm production in mice and men.

But she said the process of developing such a drug could still be very long.